1. Field of the Invention
The present invention relates to spin-valve magnetoresistive elements exhibiting variable electrical resistance in response to the relationship between the magnetization vector of a free magnetic layer and the magnetization vector of a pinned magnetic layer, relates to thin-film magnetic heads provided therewith, and relates to methods for making the same. In particular, the present invention relates to a structure of a spin-valve magnetoresistive element having two separated pinned magnetic layers and relates to a technology for reducing asymmetry when a detecting current magnetic field is applied.
2. Description of the Background
Anisotropic magnetoresistive (AMR) heads using anisotropic magnetoresistive effects and giant magnetoresistive (GMR) heads using spin-dependent scattering phenomena of conduction electrons are known as magnetoresistive reading (MR) heads. One of the known GMR heads is a spin-valve head exhibiting a high magnetoresistive effect with respect to a low external magnetic field.
FIG. 22 is a cross-sectional view of a conventional spin-valve magnetoresistive element when viewed from a face opposing a recording medium. In this spin-valve magnetoresistive element, an antiferromagnetic layer 102 and a pinned magnetic layer 103 are deposited on a substrate 101, in that order. The pinned magnetic layer 103 is in contact with the antiferromagnetic layer 102, and an exchange coupling magnetic field (exchange anisotropic magnetic field) is generated at the interface between the pinned magnetic layer 103 and the antiferromagnetic layer 102. The pinned magnetic layer 103 is magnetized, for example, in the Y direction in the drawing.
A nonmagnetic conductive layer 104 composed of copper or the like is formed on the pinned magnetic layer 103, and free magnetic layer 105 is formed on the nonmagnetic conductive layer 104. Hard biasing layers 106 formed of, for example, a cobalt-platinum (CoPt) alloy, are formed on both sides of the free magnetic layer 105 and are magnetized in the X direction in the drawing so that the free magnetic layer 105 is aligned to a single-domain state in the X direction. Thus, the variable magnetization of the free magnetic layer 105 and the pinned magnetization of the pinned magnetic layer 103 are substantially orthogonal to each other. Current lead layers 108 are provided on the hard biasing layers 106.
In this spin-valve magnetoresistive element, a detecting current (sensing current) from the current lead layers 108 flows in the element. When the magnetization vector of the free magnetic layer 105 varies with a fringing magnetic field from a magnetic recording medium such as a hard disk, the electrical resistance varies due to the relationship with the pinned magnetization direction of the pinned magnetic layer 103. Thus, the spin-valve magnetoresistive element detects the fringing magnetic field from the magnetic recording medium as a variable voltage due to the variable electrical resistance.
It is preferable that asymmetry of the output waveform be as small as possible in the spin-valve magnetoresistive element. The asymmetry is determined by the relationship between the variable magnetization vector of the free magnetic layer 105 and the pinned magnetization vector of the pinned magnetic layer 103. When no external magnetic field is applied, it is preferable that the variable magnetization vector of the free magnetic layer 105 be orthogonal to the pinned magnetization vector of the pinned magnetic layer 103.
With reference to a schematic view in shown in FIG. 23, the variable magnetization vector of the free magnetic layer 105, which affects the output asymmetry, will be described. In the spin-valve magnetoresistive element, which reads magnetic information with a detecting current, the magnetization of the free magnetic layer 105 is affected by a demagnetizing field (dipole magnetic field) Hd generated by the magnetization Mp of the pinned magnetic layer 103, a detecting current magnetic field (sensing current magnetic field) Hj due to the detecting current J, and an interactive magnetic field Hint due to interlayer interaction between the free magnetic layer 105 and the pinned magnetic layer 103 (a magnetic field, which affects so that the magnetization of the pinned magnetic layer 103 and the magnetization of the free magnetic layer 105 are parallel to each other).
It is considered that the asymmetry is reduced when these magnetic fields are relatively small with respect to the variable magnetization Mf of the free magnetic layer 105. Thus, when no external magnetic field is applied, canceling these magnetization vectors, as represented by the following equation, minimizes the asymmetry:
Hj+Hd+Hint=0 
As shown in FIG. 23, the magnetization of the free magnetic layer 105, the detecting current magnetic field Hj and the interactive magnetic field Hint are in the same direction, whereas the demagnetizing field Hd is in a different direction. Thus, in order to minimize the asymmetry, such a spin-valve magnetoresistive element is preferably produced so as to satisfy the equation Hd=Hj+Hint based on the above relationship.
With reference to FIGS. 25A to 25E, a method for making a spin-valve magnetoresistive element of a composite ferri-pinned structure shown in FIG. 24 will be described. As shown in FIG. 24, in the composite ferri-pinned structure, the pinned magnetic layer is divided into a first pinned magnetic layer 111 and a second pinned magnetic layer 112. In FIGS. 25A to 25E, only an antiferromagnetic layer 110, the first pinned magnetic layer 111, the second pinned magnetic layer 112, and a free magnetic layer 113 are depicted for simplicity, and thus a nonmagnetic interlayer provided between the first pinned magnetic layer 111 and the second pinned magnetic layer 112 and a nonmagnetic conductive layer provided between the second pinned magnetic layer 112 and the free magnetic layer 113 are not depicted. Moreover, the depicted layers are shifted to show magnetization vectors of these layers. The magnetic thickness of the first pinned magnetic layer 111 is smaller than the magnetic thickness of the second pinned magnetic layer 112 in which the magnetic thickness corresponds to the product of the intensity of the magnetization and the thickness.
The spin-valve magnetoresistive element shown in FIG. 24 is produced as follows. The antiferromagnetic layer 110 composed of PtMn or the like, the first pinned magnetic layer 111 composed of Co or the like, the nonmagnetic interlayer (not shown in the drawing), the second pinned magnetic layer 112 composed of Co or the like, the nonmagnetic conductive layer (not shown in the drawing), and the free magnetic layer 113 composed of NiFe or the like are deposited on a substrate to form a composite. In this process, the first pinned magnetic layer 111 and the second pinned magnetic layer 112 are deposited while a magnetic field is applied in a direction perpendicular to the track width direction, then the nonmagnetic conductive layer is formed. Moreover, the first pinned magnetic layer 111 is formed while a magnetic field is applied in the track width direction. As a result, as shown in FIG. 25A, the magnetization vector of the first pinned magnetic layer 111 and the magnetization vector of the second pinned magnetic layer 112 are orthogonal to the magnetization vector of the free magnetic layer 113.
With reference to FIG. 25B, the composite is annealed while an annealing magnetic field H100 of 400 kA/m or more, which is perpendicular to the track width direction, is applied so that the PtMn antiferromagnetic layer 110 has an ordered structure. After the annealing, an intense exchange coupling magnetic field (exchange anisotropic magnetic field) occurs at the interface between the PtMn antiferromagnetic layer 110 and the first pinned magnetic layer 111. As a result, the magnetization vector of the first pinned magnetic layer 111 is pinned in the direction of the annealing magnetic field H100, which is perpendicular to the track width direction. After the annealing magnetic field is removed, the magnetization vector of the second pinned magnetic layer 112 is pinned in a direction, which is opposite to the annealing magnetic field H100, due to an exchange coupling magnetic field generated between the first pinned magnetic layer 111 and the second pinned magnetic layer 112 by the RKKY interaction. Moreover, this annealing in the magnetic field aligns the vector of the magnetic anisotropy in the free magnetic layer 113 in a direction perpendicular to the track width direction as shown in FIG. 25B.
With reference to FIG. 25C, the composite is annealed while an annealing magnetic field H200 is applied in the track width direction so that the vector of the uniaxial anisotropy is aligned along the annealing magnetic field H200. As a result, the magnetization vector of the first pinned magnetic layer 111 and the magnetization vector of the second pinned magnetic layer 112 are orthogonal to the anisotropic magnetic field of the free magnetic layer 113. The vector of the annealing magnetic field H200 may be either the right or the left.
In the single pinned magnetic layer configuration shown in FIG. 23, the demagnetizing field is large at edges of the element. Thus, a leakage magnetic field to the exterior is large, and the pinning force acting from the antiferromagnetic layer 102 to the pinned magnetic layer 103 is not large. The spin-valve magnetoresistive element having the composite ferri-pinned structure shown in FIG. 24 has been developed to solve the above problem. As shown in FIG. 24, the magnetization vector of the first pinned magnetic layer 111 and the magnetization vector of the second pinned magnetic layer 112 are antiparallel to each other and the magnetic moment of one of these is larger than the magnetic moment of the other. Thus, a strong pinning force is achieved by an effective magnetostatic coupling magnetic field from the antiferromagnetic layer 110 to these two pinned magnetic layers.
In the spin-valve magnetoresistive element of the composite ferri-pinned structure shown in FIG. 24, the fringing magnetic field of the first pinned magnetic layer compensates for most of the fringing magnetic field of the two pinned magnetic layers to reduce the effect of the demagnetizing field (dipole magnetic field) Hd on the free magnetic layer 113. Since the demagnetizing field Hd is reduced in such a mechanism, the detecting current magnetic field Hj is larger than the demagnetizing field Hd. Thus, it is difficult to reduce the asymmetry since the detecting current magnetic field Hj is too large to compensate for the demagnetizing field Hd. In particular, when the demagnetizing field Hd is small in the composite structure shown in FIG. 24, the detecting current magnetic field Hj affects the magnetization vector of the free magnetic layer 105. That is, the magnetization vector of the free magnetic layer 105 tilts toward the lower right side, as shown by the vector Mf1 in FIG. 24. As a result, the orthogonal magnetizations of the first pinned magnetic layer 111 and the second pinned magnetic layer 112 are not achieved.
When the demagnetizing field Hd is increased so as to be balanced with the detecting current magnetic field Hj in order to reduce asymmetry, the pinning force of the antiferromagnetic layer 110 to the first pinned magnetic layer 111 and the second pinned magnetic layer 112 is decreased. Accordingly, the control of the asymmetry in the spin-valve magnetoresistive element having the composite ferri-pinned structure requires another mechanism.
A thin-film magnetic head having the spin-valve magnetoresistive element as a reading element generally has a composite configuration including an inductive element (magnetic inductive head) as a writing element. The write head has an inductive coil for recording, and a magnetic pole for writing formed of a magnetic film and a magnetic gap provided at the edge of the inductive coil. An insulating layer formed of resin is provided to insulate the inductive coil from other layers. In the formation of the insulating resin layer for covering the inductive coil, an uncured resin is applied and is cured by heat. After the uniaxial anisotropy is imparted to the free magnetic layer 113 as shown in FIG. 25C, the write head is formed, and then these are annealed together with an upper shield 114 and a lower shield 115. The annealing temperature exceeds 473 K (200xc2x0 C.) for achieving curing of the resin. Such a high annealing temperature disorders the uniaxial anisotropy in the free magnetic layer 113, resulting in the generation of Barkhausen noise, as shown in FIG. 25E. Thus, the reading head does not have desired characteristics.
In the thin-film magnetic head, the upper shield 114 provided on the magnetoresistive element also functions as a lower core layer of the write head (inductive head). When disorder of the uniaxial anisotropy in the free magnetic layer 113 and the disorder of the magnetization easy axis in the upper shield 114 simultaneously occur in such a configuration, the magnetization, that is, the magnetic domain structure, of the upper shield 114 is irreversibly varied with recording of magnetic information on a magnetic recording medium by the inductive head. An unstable magnetic field generated by the irreversible magnetic domain will result in unstable read output from the magnetoresistive element.
It is an object of the present invention to provide a spin-valve magnetoresistive element exhibiting reduced asymmetry in which the magnetization vectors of pinned magnetic layers and a free magnetic layer are aligned to predetermined directions when a detecting current magnetic field is applied.
It is another object of the present invention to provide a thin-film magnetic head using the spin-valve magnetoresistive element.
It is another object of the present invention to provide a spin-valve magnetoresistive element having a composite ferri-pinned structure which exhibits reduced asymmetry, a thin-film magnetic head having the spin-valve magnetoresistive element, a method for making the spin-valve magnetoresistive element, and a method for making the thin-film magnetic head.
It is another object of the present invention to provide a spin-valve magnetoresistive element exhibiting reduced asymmetry in which the directions of applied magnetic fields are adjusted when individual layers are magnetized in response to the relationship between the magnetic thickness of the first pinned magnetic layer and the magnetic thickness of the second pinned magnetic layer.
According to a first aspect of the present invention, a spin-valve magnetoresistive element includes: an antiferromagnetic layer; a first pinned magnetic layer in contact with the antiferromagnetic layer, an exchange anisotropic magnetic field being formed between the antiferromagnetic layer and the first pinned magnetic layer for pinning the magnetization vector of the first pinned magnetic layer; a nonmagnetic interlayer; a second pinned magnetic layer, the nonmagnetic interlayer being disposed between the first pinned magnetic layer and the second pinned magnetic layer, the magnetization vector of the second pinned magnetic layer being aligned in a direction antiparallel to the magnetization vector of the first pinned magnetic layer; a nonmagnetic conductive layer in contact with the second pinned magnetic layer; a free magnetic layer in contact with the nonmagnetic conductive layer; longitudinal biasing layers for applying a longitudinal biasing magnetic field in a track width direction to the free magnetic layer; and a pair of lead layers for supplying a detecting current to the second pinned magnetic layer, the nonmagnetic conductive layer, and the free magnetic layer; wherein, when the detecting current is supplied from the lead layers, the magnetization vector of the free magnetic layer is aligned in a direction intersecting the magnetization vector of the second pinned magnetic layer, and the magnetization vector of the second pinned magnetic layer is tilted from the direction perpendicular to the track width direction toward a direction opposite to the longitudinal biasing magnetic field.
When the detecting current is applied, the magnetization vector of the free magnetic layer and the magnetization vectors of the pinned magnetic layers intersect with a predetermined angle. This configuration produces a large change in resistance when an external magnetic field is applied from a magnetic recording medium compared to a state where no external magnetic field is applied. Moreover, the asymmetry of the output from the magnetic information on a magnetic recording medium is reduced.
According to a second aspect of the present invention, a spin-valve magnetoresistive element includes an antiferromagnetic layer; a first pinned magnetic layer in contact with the antiferromagnetic layer, an exchange anisotropic magnetic field being formed between the antiferromagnetic layer and the first pinned magnetic layer for pinning the magnetization vector of the first pinned magnetic layer; a nonmagnetic interlayer; a second pinned magnetic layer, the nonmagnetic interlayer being disposed between the first pinned magnetic layer and the second pinned magnetic layer, the magnetization vector of the second pinned magnetic layer being aligned in a direction antiparallel to the magnetization vector of the first pinned magnetic layer; a nonmagnetic conductive layer in contact with the second pinned magnetic layer; a free magnetic layer in contact with the nonmagnetic conductive layer; longitudinal biasing layers for applying a longitudinal biasing magnetic field in a track width direction to the free magnetic layer; and a pair of lead layers for supplying a detecting current to the second pinned magnetic layer, the nonmagnetic conductive layer, and the free magnetic layer; wherein, when the detecting current is supplied from the lead layers, the magnetization vector of the free magnetic layer is aligned in a direction intersecting the magnetization vector of the second pinned magnetic layer, and the magnetization vector of the free magnetic layer is tilted from the track width direction toward the magnetization vector of the second pinned magnetic layer.
When the detecting current is applied, the magnetization vector of the free magnetic layer and the magnetization vectors of the pinned magnetic layers intersect with a predetermined angle. Thus, the asymmetry of the output from the magnetic information on a magnetic recording medium is reduced.
In the first and second aspects, the angle of tilt of the free magnetic layer, xcex8, is preferably in a range of 2xc2x0 to 30xc2x0, more preferably 3xc2x0 to 15xc2x0, and most preferably 3xc2x0 to 10xc2x0. The asymmetry can be more effectively reduced within the range without reducing the output. At an angle exceeding this range, the output is reduced. At an angle of less than this range, the asymmetry is not significantly improved.
When the detecting current is supplied and when no external magnetic field is applied, the angle defined by the magnetization vector of the free magnetic layer and the magnetization vector of the second pinned magnetic layer is preferably 90xc2x0. The magnetization vector of the free magnetic layer is tilted by the effect of the detecting current magnetic field due to the detecting current. Since the magnetization vector of the second pinned magnetic layer and the tilted magnetization vector of the second pinned magnetic layer are orthogonal to each other, the asymmetry is most effectively reduced while maintaining high output.
Preferably, the magnetic thickness of the first pinned magnetic layer is smaller than the magnetic thickness of the second pinned magnetic layer, the direction of the detecting current magnetic field applied to the free magnetic layer is opposite to the magnetization vector of the second pinned magnetic layer, and the direction of the detecting current magnetic field applied to the second pinned magnetic layer is opposite to the magnetization vector of the second pinned magnetic layer, where the magnetic thickness is defined as the product of the saturation magnetization and the thickness. This configuration stabilizes the magnetization vector of the first pinned magnetic layer and the magnetization vector of the second pinned magnetic layer, and produces a large change rate of resistance xcex94R/R.
Preferably, the antiferromagnetic layer includes one of an XMn alloy and an XMnXxe2x80x2 alloy, wherein X is at least one element selected from the group consisting of Pt, Pd, Rh, Ir, Ru, and Os, and Xxe2x80x2 is at least one element selected from the group consisting of Au, Ag, Cr, Ni, Ne, Ar, Xe, and Kr.
Since these alloys have higher blocking temperatures than those of conventional antiferromagnetic materials such as FeMn, the resulting spin-valve magnetoresistive element is thermally stable.
Preferably, the overall exchange anisotropic magnetic field of the antiferromagnetic layer affecting a composite pinned magnetic layer including the first pinned magnetic layer and the second pinned magnetic layer is 96 kA/m or more. When the overall exchange anisotropic magnetic field has such a high value, a hard biasing magnetic field from the longitudinal biasing layers does not extraordinarily tilt the magnetization of the pinned magnetic layer at the peripheral portions.
Preferably, the antiferromagnetic layer, the first pinned magnetic layer, the nonmagnetic interlayer, the second pinned magnetic layer, and the free magnetic layer are deposited in that order on a substrate. In the bottom-type spin-valve magnetoresistive element in which the antiferromagnetic layer is deposited near the substrate, the anisotropic magnetic field of the pinned magnetic layer can be increased.
Preferably, the free magnetic layer comprises a first free magnetic layer and a second free magnetic layer separated by a conductive interlayer provided therebetween.
Alternatively, the free magnetic layer, the nonmagnetic conductive layer, the second pinned magnetic layer, the conductive interlayer, the first pinned magnetic layer, and the antiferromagnetic layer are deposited in that order on a substrate.
According to a third aspect of the present invention, a method for making a spin-valve magnetoresistive element includes: a composite forming step for forming a composite having an antiferromagnetic layer, a first pinned magnetic layer, a nonmagnetic interlayer, a second pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer on a substrate, the free magnetic layer being formed while applying a first magnetic field in one of a first direction along a track width direction and a direction opposite to the first direction to impart uniaxial anisotropy in the track width direction to the free magnetic layer; a first annealing step for annealing the composite at a first annealing temperature while applying a second magnetic field in one of a second direction tilted by an angle xcex8 from the normal of the track width direction and a third direction opposite to the second direction to generate an exchange anisotropic magnetic field at the interface between the antiferromagnetic layer and the first pinned magnetic layer, to pin the magnetization of the first pinned magnetic layer and the magnetization of the second pinned magnetic layer in directions which are tilted by the angle xcex8 from the normal of the track width direction and which are antiparallel to each other; a biasing layer forming step for forming longitudinal biasing layers, for applying a biasing magnetic field to the free magnetic layer, on both sides of the laminate; a second annealing step for annealing the laminate at a second annealing temperature while applying a third magnetic field to the free magnetic layer in one of the first direction and a direction opposite to the first direction to impart uniaxial anisotropy to the free magnetic layer; and a biasing layer magnetizing step for applying a fourth magnetic field in a fourth direction opposite to the component in the track width direction of the magnetization vector of the second pinned magnetic layer to magnetize the longitudinal biasing layers.
The first annealing step at the first annealing temperature while applying the second magnetic field in the second direction pins the magnetization vector of the first pinned magnetic layer with a tilt angle xcex8. Next, the uniaxial anisotropy of the free magnetic layer is aligned in the track width direction during the second annealing step so that the magnetization vector of the pinned magnetic layer and the free magnetic layer intersect each other when the detecting current magnetic field is applied.
When the magnetic thickness of the first pinned magnetic layer is smaller than the magnetic thickness of the second pinned magnetic layer, the intensity of the second magnetic field may be 400 kA/m or more so as to align the magnetization vector of the first pinned magnetic layer in the second direction and the magnetization vector of the second pinned magnetic layer in the third direction, or the intensity of the second magnetic field may be 8 to 80 kA/m so as to align the magnetization vector of the first pinned magnetic layer in the third direction and the magnetization vector of the second pinned magnetic layer in the second direction, where the magnetic thickness is defined as the product of the magnetic moment and the thickness of the corresponding pinned magnetic layer.
When the magnetic thickness of the first pinned magnetic layer is larger than the magnetic thickness of the second pinned magnetic layer, the intensity of the second magnetic field may be 400 kA/m or more so as to align the magnetization vector of the first pinned magnetic layer in the second direction and the magnetization vector of the second pinned magnetic layer in the third direction, or the intensity of the second magnetic field may be 8 to 80 kA/m so as to align the magnetization vector of the first pinned magnetic layer in the second direction and the magnetization vector of the second pinned magnetic layer in the second direction, where the magnetic thickness is defined as the product of the magnetic moment and the thickness of the corresponding pinned magnetic layer.
The method for making a spin-valve magnetoresistive element may further comprises a recording head annealing step for forming an inductive recording magnetic head onto the composite, the recording head annealing step being provided between the first annealing step and the second annealing step. The annealing step for forming the inductive recording magnetic head disorders the uniaxial anisotropy of the free magnetic layer, but the subsequent second annealing step aligns the uniaxial anisotropy of the free magnetic layer. Thus, the spin-valve magnetoresistive element has a uniaxially anisotropic free magnetic layer.
The method for making a spin-valve magnetoresistive element may further comprise an additional annealing step, prior to the recording head annealing step, for annealing the composite while applying a magnetic field to the free magnetic layer in one of the first direction and the direction opposite to the first direction to impart uniaxial anisotropy in the track width direction to the free magnetic layer.
Preferably, the third magnetic field applied in the second annealing step is smaller than the second magnetic field applied in the first annealing step. Since the third magnetic field is smaller than the second magnetic field, the uniaxial anisotropy of the free magnetic layer is aligned without adversely affecting the magnetization vector of the pinned magnetic layer.
Preferably, the intensity of the third magnetic field applied in the second annealing step is 8 kA/m to 40 kA/m.
Preferably, the first annealing temperature is in a range of 230xc2x0 C. (503 K) to 280xc2x0 C. (553 K) and the second annealing temperature is in a range of 160xc2x0 C. (433 K) to 240xc2x0 C. (513 K).
Preferably, the antiferromagnetic layer includes one of an XMn alloy and an XMnXxe2x80x2 alloy wherein X is at least one element selected from the group consisting of Pt, Pd, Rh, Ir, Ru, and Os, and Xxe2x80x2 is at least one element selected from the group consisting of Au, Ag, Cr, Ni, Ne, Ar, Xe, and Kr.
The antiferromagnetic layer may be disposed between the substrate and the free magnetic layer in the composite.
According to a fourth aspect of the present invention, a method for making a spin-valve magnetoresistive element includes: a composite forming step for forming a composite having an antiferromagnetic layer, a first pinned magnetic layer, a nonmagnetic interlayer, a second pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer on a substrate, the free magnetic layer being formed while applying a first magnetic field in one of a first direction along a track width direction and a direction opposite to the first direction to impart uniaxial anisotropy in the track width direction to the free magnetic layer; a first annealing step for annealing the composite at a first annealing temperature while applying a second magnetic field in a second direction orthogonal to the track width direction to generate an exchange anisotropic magnetic field at the interface between the antiferromagnetic layer and the first pinned magnetic layer so as to pin the magnetization of the first pinned magnetic layer and the magnetization of the second pinned magnetic layer in a direction orthogonal to the track width direction; a biasing layer forming step for forming longitudinal biasing layers, for applying a biasing magnetic field to the free magnetic layer, on both sides of the laminate; a second annealing step for annealing the laminate at a second annealing temperature while applying a third magnetic field to the free magnetic layer in one of the first direction and a direction opposite to the first direction to impart uniaxial anisotropy to the free magnetic layer and to tilt by an angle xcex8 from the normal of the track width direction the magnetization vector of the first pinned magnetic layer and the magnetization vector of the second pinned magnetic layer; and a biasing layer magnetizing step for applying a fourth magnetic field in a fourth direction opposite to the component in the track width direction of the magnetization vector of the second pinned magnetic layer to magnetize the longitudinal biasing layers.
The first annealing step while applying the second magnetic field in the second direction pins the magnetization vector of the first pinned magnetic layer in contact with the antiferromagnetic layer and the magnetization vector of the second pinned magnetic layer in a direction orthogonal to the track width direction. The subsequent annealing in the magnetic field applied in the track width direction tilts the magnetization vectors of the pinned magnetic layers by an angle xcex8 from the direction orthogonal to the track width direction. Thus, in the spin-valve magnetoresistive element, the magnetization vectors of the pinned magnetic layers and the magnetization vector of the free magnetic layer intersect each other when a dipole magnetic field is applied.
When the magnetic thickness of the first pinned magnetic layer is larger than the magnetic thickness of the second pinned magnetic layer, the magnetization vector of the first pinned magnetic layer is aligned in the second direction, and the magnetization vector of the second pinned magnetic layer is aligned in a direction opposite to the second direction, where the magnetic thickness is defined as the product of the magnetic moment and the thickness of the corresponding pinned magnetic layer.
When the magnetic thickness of the first pinned magnetic layer is larger than the magnetic thickness of the second pinned magnetic layer, the intensity of the second magnetic field may be 400 kA/m or more so as to align the magnetization vector of the first pinned magnetic layer in the second direction and the magnetization vector of the second pinned magnetic layer in a third direction opposite to the second direction, or the intensity of the second magnetic field may be 8 to 80 kA/m so as to align the magnetization vector of the first pinned magnetic layer in the second direction and the magnetization vector of the second pinned magnetic layer in the third direction, where the magnetic thickness is defined as the product of the magnetic moment and the thickness of the corresponding pinned magnetic layer.
When the magnetic thickness of the first pinned magnetic layer is smaller than the magnetic thickness of the second pinned magnetic layer, the intensity of the second magnetic field may be 400 kA/m or more so as to align the magnetization vector of the first pinned magnetic layer in the second direction and the magnetization vector of the second pinned magnetic layer in a third direction opposite to the second direction, or the intensity of the second magnetic field may be 8 to 80 kA/m so as to align the magnetization vector of the first pinned magnetic layer in the third direction and the magnetization vector of the second pinned magnetic layer in the second direction, where the magnetic thickness is defined as the product of the magnetic moment and the thickness of the corresponding pinned magnetic layer.
The method for making a spin-valve magnetoresistive element may further include a recording head annealing step for forming an inductive recording magnetic head onto the composite, the recording head annealing step being provided between the first annealing step and the second annealing step. The annealing step for forming the inductive recording magnetic head disorders the uniaxial anisotropy of the free magnetic layer, but the subsequent second annealing step aligns the uniaxial anisotropy of the free magnetic layer. Thus, the spin-valve magnetoresistive element has a uniaxially anisotropic free magnetic layer.
Preferably, the third magnetic field applied in the second annealing step is smaller than the second magnetic field applied in the first annealing step.
Preferably, the first annealing temperature is in a range of 230xc2x0 C. (503 K) to 280xc2x0 C. (553 K) and the second annealing temperature is in a range of 160xc2x0 C. (433 K) to 240xc2x0 C. (513 K).
Preferably, the antiferromagnetic layer includes one of an XMn alloy and an XMnXxe2x80x2 alloy wherein X is at least one element selected from the group consisting of Pt, Pd, Rh, Ir, Ru, and Os, and Xxe2x80x2 is at least one element selected from the group consisting of Au, Ag, Cr, Ni, Ne, Ar, Xe, and Kr.
The antiferromagnetic layer may be disposed between the substrate and the free magnetic layer in the composite.
In the present invention, a thin-film magnetic head is produced by a step for forming a spin-valve magnetoresistive element as a read element and by a step for forming an inductive read magnetic head on the spin-valve magnetoresistive element.